爷爷以卖上等木材为生父亲以卖劈柴和柴墩为生儿子以卖根雕原料为生孙子以卖黄沙为生

　　例文： Preserving Natural Resources

　　Through the changes in the ways of making a living in a family over several generations, the cartoon aims at sounding a warning against man“s wasteful use of natural resources and emphasizing the urgent need to preserve these resources.

　　Ever since man appeared on the earth, man“s survival has been heavily relied on nature. Almost everything we use in our everyday life comes from nature, ranging from the food we eat, the water we drink, to the wood which is turned into furiture. With the development of technology and population growth, the amount and range of materials used has increased at an alarming rate. However, natural resources are not inexhaustible. Some reserves are already on the brink of exhaustion and there is no hope of replacing them. The widespread water shortage is an example in point. If man continued to squander natural resources with no thought for the future, the later generations would end up selling sand, as is the case in the cartoon, and the whole world would be in a mess.

　　Time is running out. It is up to us to take effective measures before the situation gets out of hand.

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